The most common joining mechanism for tractor trailers in the United States involves the use of a kingpin at the front end of the trailer to connect with the fifth wheel on the tractor. A kingpin inserts into the fifth wheel of a tractor which then, after locking, pulls the trailer across the roads and highways to deliver the goods in the trailer. Essentially all of the trailer weight pulled by the tractor is transferred across the kingpin, so the kingpin is under a great amount of stress. It also is subject to wear. When a kingpin wears beyond a certain point it creates a risk that the trailer will become accidentally disconnected from the tractor. In addition to routine wear, a kingpin may be impacted and thereby angled beyond a desired or allowed tolerance. Excessive wear and/or specific damage present risks of both damage to goods and possible harm to individuals, that is, injury or loss of life.
FIG. 1 provides a side view of a common style of kingpin 10; other styles are known in the art and the differences in style are not known to affect the operation of the present invention. The kingpin 10 typically is secured by welding (welds not shown) of its upper portion 15 onto a solid plate 18 of the trailer (such as a trailer “bolster plate”). Once so installed, the parts of the kingpin 10 viewable from outside the trailer, and those involved with joining to the fifth wheel of a tractor, are: a cylindrical base 20 having a height 25; a cylindrical shank 30 having a height 35; and a cylindrical head 40, which is the bottom-most component of the kingpin 10, having a height 45. In use, the kingpin 10 is vertically oriented, as indicated by vertical axis 50. When in use by insertion into a tractor fifth wheel, the kingpin experiences most wear on shank 30.
The size of kingpins most commonly found in trailers in use in the United States is a nominal 2-inch kingpin. For such a kingpin, the base has a 2.875 inch diameter, the shank has a 2 inch diameter, and the head has a 2.810 inch diameter. A larger, 3-inch nominal size kingpin, is used for certain large equipment trailers.
While replacement of kingpins is known in the art, newer technologies provide for on-site rebuild of kingpins (see, for example, www.kingpinspecialists.com). The advantages of on-site rebuilding include: lower cost; faster turnaround time; and less time and miles driving on the road with an excessively worn kingpin. Whether worn or damaged, a kingpin that has exceeded allowed specifications presents an undesired risk (including violation of regulations and/or guidelines) when that kingpin remains in use on the road, such as to pull a trailer (bearing that kingpin) to a shop for replacement or repair. Consequently, there is a need to accurately and precisely predict the status of wear of a kingpin.
Thus, there is a need to monitor and assess the condition of kingpins by mechanics and other personnel. In the past, this has been done by using gauges of various sorts. For example, a plastic gauge provided by The Holland Group, Inc., (Holland, Mich.) measures both the 2-inch and the 3-inch sizes of kingpins. However, for each of the base and shank diameters, the gauge only indicates whether the respective diameter has worn to the point of needing replacement or rebuilding. That is, it has no provision for indicating that the respective diameter is close to requiring replacement or rebuilding. Also, the plastic is flexible and has been found to deform during use, reducing the accuracy and precision of measurements taken by the Holland gauge. This plastic gauge also has means for measuring the length of the kingpin.
Another gauge is comprised of thin metal and has an opening that provides spaced but converging sides (i.e., a truncated cone, resembling a portion of the two equal sides of an isosceles triangle). The kingpin component is slid between these sides, and measurements provided along the sides are supposed to allow assessment by a user as to the wear status of the kingpin. However, given the grease typically found on a kingpin, and the difficult position of a kingpin, beneath the front section of a trailer, taking such readings accurately and precisely is not easy for this style of gauge. Both the other style of gauges (i.e., plastic with no intermediate notch and the thin metal with triangular groove) have a tendency to stretch or otherwise deform when rotated around an unevenly worn kingpin.
Thus, the present inventor has recognized problems with gauges provided in the industry and has conceived of, and put into practice, a solution to such problems. The present inventor has developed an improved gauge for use by truck drivers, mechanics and other personnel involved in the tractor trailer industry. This gauge provides for more accurate and precise measurements of the various dimensions and components of a trailer kingpin, and also provides for a new, intermediate measurement that provides a result that indicates the kingpin is near a point of wear that would exceed a desired acceptability specification. This allows the user to schedule replacement or rebuild of the kingpin without having to drive with a kingpin that has already gone out of specification (or to take the trailer out of commission until a rebuild or replacement can be scheduled). This is also useful because the more wear there is on the kingpin, the faster the kingpin wears the jaws of the fifth wheel.